1. Field of the Invention
The present invention relates generally to two-dimensional phased-array transducers and, more particularly, to two-dimensional ultrasound phased array transducers.
2. Related Art
Diagnostic ultrasound is used in many different fields of technology as a non-invasive method of determining the internal structure of an object. Diagnostic ultrasound, for example, is used in various medical specialties, such as obstetrics, cardiology and radiology, and may be used in other diverse fields, such as in metallurgy to determine the patency of a weld, etc.
Medical ultrasound scanners typically use a Nx1 linear array of transducer elements. Ultrasound energy transmitted and received by the array may be electronically steered and focused using known phased array techniques. One conventional transducer is illustrated in FIGS. 1 and 2. As shown in FIG. 1, a typical transducer array 1 is formed on an acoustic backing 10 that serves to isolate acoustically individual transducer elements 5. A piezoelectric layer 16 is formed on the acoustic backing 10. Typically the piezoelectric layer 16 is formed of a material such as lead zirconate titanate (PZT). An electrically conductive acoustic matching layer 18 is formed on top of the piezoelectric layer 16, and a ground plane 20 is formed on top of the matching layer 18. Interconnect wires 26 along one side of the acoustic backing 10 connect the individual transducer elements 5 to processing electronics. After the laminate structure is formed but before the ground plane 20 is formed, kerfs 40 are formed through the laminate into the backing 10, between interconnect wires 26, to separate the laminate structure into a plurality of parallel ultrasound transducer elements 5. Typically, ultrasound transducer elements are approximately 0.2 mm wide and 10 mm long. The ultrasound transducer array 1 is typically disposed in a user manipulable probe having a handle for grasping by the user. The probe is connected to the electronics portion of an ultrasound imaging system via a cable.
Linear arrays can focus an ultrasound beam in two dimensions using known phased array techniques. Thus a linear array is able to acquire data representing a two-dimensional slice through the object to be analyzed. To expand the capabilities of diagnostic ultrasound, experimentation has been conducted using two-dimensional ultrasound arrays. Using phased array techniques, two-dimensional ultrasound arrays have the potential of being able to compensate for tissue inhomogeneities or aberrations, to enable the beam to be steered in three dimensions and to thereby acquire three-dimensional images, and may be useful for calculating volumes within the object to be analyzed.
Unfortunately, fabrication of a two-dimensional ultrasound phased array transducer using the above-described manufacturing techniques is not trivial. It is necessary to connect each individual element of a two-dimensional phased array ultrasound transducer to associated circuitry. Since fabrication of the individual two-dimensional ultrasound phased array transducer elements involves cutting a kerf through the piezoelectric layer and into the backing layer in “X” and “Y” directions, it is not possible to simply form traces on the backing layer, as was done for one-dimensional arrays, since the traces would be severed during the kerf formation process (also called dicing). In addition, the extremely small size of the transducer elements complicates the manufacturing process.
Accordingly, it would be advantageous to provide a two-dimensional phased array ultrasound transducer that is simple to manufacture, while allowing the elements of the array to be connected individually to associated processing circuitry. It would also be advantageous to provide a simple manufacturing process for producing a two-dimensional phased array transducer.